Why do we use identical (paired) tyres?

[Vantage]

Once more we can find a bit of myth debunking on Jan Hein's website.

https://www.renehersecycles.com/myth-6- ... -the-road/

A quote:

"There is another way to increase the interlocking between tire and road: provide edges on the tire that ‘hook up’ with the road surface irregularities. Each edge provides a point where a road irregularity can hook up. The more edges you have, the better the tire hooks up".

In other words, tread on a tire can improve it's grip to the road - nothing to do with aquaplaning avoidance in that, you see.

In my own experience, I found that the use of a Schwalbe G-One tyre (those with the wee round knobbles all over them) made a difference to the traction I was able to get from strong thrusts through the pedals laid down on those often wet & slimy back roads found during the autumn and winter months. I was spinning the back wheel on such roads when going up a steep slope with a back tyre of the non-treaded kind (a Schwalbe One). The G-One of the same width at the same pressure seems to get a better grip and doesn't spin out nearly so readily. In fact, not at all, so far.

Sliding out sideways on such roads never seemed an issue with slick tyres, though. So, although I had a pair of G-One knobblers on the winter bike, I suspect that just the one on the back was needed to avoid wheel-spin. There's a case for different front & back tyres, I suppose.

Cugel

Someone should correct the worlds F1 teams then.
You don't think the rubber on a tyre is supple enough to mould itself around the rough edges of a road?
Cutting tread into a tyre removes the rubber which would otherwise be providing grip.
My Voyager Hypers have a very shallow tread. I'm pretty sure it's only there to look pretty to entice clueless types into believing it serves a purpose. Same tyres provide more than adequate traction to get me up and down 10%+ dirt tracks in the wet.
Tread on a road bike? Not worth the rubber it lacks.

[mattheus]

With regard to road tyres, I can't see any point in specific front/rear tyres as the only difference would be tread pattern. As we know, tread on a bicycle road tyre is pointless. The tyres aren't wide enough and the bike won't go fast enough for aquaplaning to be an issue. I can see some benefit for a rear tyre being more heavily built for the extra weight on it but other than that, I can't see the point.

Once more we can find a bit of myth debunking on Jan Hein's website.

https://www.renehersecycles.com/myth-6- ... -the-road/

A quote:

"There is another way to increase the interlocking between tire and road: provide edges on the tire that ‘hook up’ with the road surface irregularities. Each edge provides a point where a road irregularity can hook up. The more edges you have, the better the tire hooks up".

In other words, tread on a tire can improve it's grip to the road - nothing to do with aquaplaning avoidance in that, you see.

Hmmm. I wonder who might be selling road tyres with edges to improve "interlocking" ...

[mig]

Once more we can find a bit of myth debunking on Jan Hein's website.

https://www.renehersecycles.com/myth-6- ... -the-road/

A quote:

"There is another way to increase the interlocking between tire and road: provide edges on the tire that ‘hook up’ with the road surface irregularities. Each edge provides a point where a road irregularity can hook up. The more edges you have, the better the tire hooks up".

In other words, tread on a tire can improve it's grip to the road - nothing to do with aquaplaning avoidance in that, you see.

In my own experience, I found that the use of a Schwalbe G-One tyre (those with the wee round knobbles all over them) made a difference to the traction I was able to get from strong thrusts through the pedals laid down on those often wet & slimy back roads found during the autumn and winter months. I was spinning the back wheel on such roads when going up a steep slope with a back tyre of the non-treaded kind (a Schwalbe One). The G-One of the same width at the same pressure seems to get a better grip and doesn't spin out nearly so readily. In fact, not at all, so far.

Sliding out sideways on such roads never seemed an issue with slick tyres, though. So, although I had a pair of G-One knobblers on the winter bike, I suspect that just the one on the back was needed to avoid wheel-spin. There's a case for different front & back tyres, I suppose.

Cugel

Someone should correct the worlds F1 teams then.
You don't think the rubber on a tyre is supple enough to mould itself around the rough edges of a road?
Cutting tread into a tyre removes the rubber which would otherwise be providing grip.
My Voyager Hypers have a very shallow tread. I'm pretty sure it's only there to look pretty to entice clueless types into believing it serves a purpose. Same tyres provide more than adequate traction to get me up and down 10%+ dirt tracks in the wet.
Tread on a road bike? Not worth the rubber it lacks.

the world's F1 teams do use treaded tyres when it's wet.

[Nearholmer]

I ride 50:50 tarmac:not, and have recently swapped from tubed touring tyres to ‘light gravel’ tubeless (I wanted the Schwalbe G1Allrounds, but couldn’t get them locally and ended-up with Bontrager GRX2).

My take is that having grip on the front tyre as well as the back makes for better control on loose ground, and is really helpful when climbing out of ruts, where a less treaded tyre will often refuse to climb up the side of the rut, so that makes me happy with the same fore and aft.

[mattheus]

the world's F1 teams do use treaded tyres when it's wet.

Surely we've already covered this?!?

[Actually their cars are quite good on slicks until there is substantial build-up - so damp/greasy tracks are fine on slicks. But more importantly:]

CAR tyres aquaplane, being much wider than bike tyres.
Hence the need for tread.

[foxyrider]

With regard to road tyres, I can't see any point in specific front/rear tyres as the only difference would be tread pattern. As we know, tread on a bicycle road tyre is pointless. The tyres aren't wide enough and the bike won't go fast enough for aquaplaning to be an issue. I can see some benefit for a rear tyre being more heavily built for the extra weight on it but other than that, I can't see the point.

Once more we can find a bit of myth debunking on Jan Hein's website.

https://www.renehersecycles.com/myth-6- ... -the-road/

A quote:

"There is another way to increase the interlocking between tire and road: provide edges on the tire that ‘hook up’ with the road surface irregularities. Each edge provides a point where a road irregularity can hook up. The more edges you have, the better the tire hooks up".

In other words, tread on a tire can improve it's grip to the road - nothing to do with aquaplaning avoidance in that, you see.

Hmmm. I wonder who might be selling road tyres with edges to improve "interlocking" ...

that'll be the old file tread so beloved in the 70's/80's!

[Sweep]

wondering, for folks who never never mix and match - do folks never find that their favoured in-use tyre is no longer available?

or never buy a tyre because it's cheap to replace a dead/too cut one?

(PlanetX's wondrous offers come to mind)

If a tyre finally gives up the ghosr do they send its loving partner to landfill as well as a death tribute?

[Nearholmer]

Might be worth considering when comparing F1 cars and pushbikes that what is going on at the tyre-road interface in the two applications might be rather different.

F1 tracks are reasonably smooth, don’t incorporate very steep slopes, and if the surface conditions deteriorated to the friction levels found on many low-status roads in winter, let alone off-road, racing would be stopped. Added to which, F1 tyre compounds are designed to run slightly warm, and most leisure cyclists don’t attain speeds that warm their tyres up.

A pure road cycling tyre, tuned for decently smooth surfaces, probably can be as near slick as makes no difference, so a bit like an F1 dry tyre, but as soon as the surface become significantly imperfect some sort of tread can help, especially one where the knobbles (think tiny ones, not MTB or tractor) actually deform as they pass through the contact patch. They can displace water or slime, and grab imperfections. The idea that cutting a tread simply puts fresh air where one wants rubber is too simplistic, for one thing it seems to assume no deformation of the tyre in the contact patch, which even for ‘rock hard’ slicks isn’t quite true, and for modern softer compound tyres run at lower pressures is very untrue.

Like Cugel I’ve experience wheel-spin when using touring tyres on very steep and very poor surfaces. I have yet to experience it with ‘tiny soft knobbles’ tyres.

[esasjl]

This is a very good question. Front and rear tyres need to grip well under user conditions. This needs to happen for -ve, +ve and angular accelerations suggesting similar tyres front and rear. Slicks (and file tread that wears quickly) seem a good choice for dry/damp, clean, sealed, and textured surfaces (tarmac, concrete) as well as metalled (gravel, dirt) roads. Higher volume tyres seem useful for higher loads and lumpier surfaces. Surfaces softer than tyre rubber, and/or deforms inelastically under drive/braking shear (grass, mud, biofilm), seem best approached with knobby tyres. Sipes and studs are better for snow (and 'stiff' mud) and ice. Studs might even grip muddy, wet polished limestone.

I use slicks on my 'road' bikes and am very happy with them. The choice is more difficult for all-road/ATB use. Large volume slicks are great on rough but clean sealed and metalled surfaces but poor on grass and softer ground. Identical tyres, but with a knobby tread (RH 26 x 2.3), are much better on soft ground. Emergency braking on harder surfaces is not quite so good. Knobbys corner on hard surfaces just as well as slicks but handling seems more 'twitchy', maybe because knobby tyres have less pneumatic trail. I've been trying to settle on the optimum general purpose setup. For this I think knobbys are better than slicks but after reading this thread it would be interesting to try mixing them to see if, say, slick front and knobby back tyres (or the reverse) provide a better balance of strengths and weaknesses.

[Vantage]

F1 tracks are reasonably smooth, don’t incorporate very steep slopes, and if the surface conditions deteriorated to the friction levels found on many low-status roads in winter, let alone off-road, racing would be stopped. Added to which, F1 tyre compounds are designed to run slightly warm, and most leisure cyclists don’t attain speeds that warm their tyres up.

Erm...Monaco? Rumble strips? Add to those the differing surfaces between tracks and they're every bit as unpredictable as public roads. Some can be quite rough such as Silverstone. Then you have the extreme G forces put through those tyres during acceleration, braking and cornering. All done without tread. Tread in fact can make the tyres disintegrate faster. You'll see wet weather F1 tyres fall apart long before their slick counterparts because the bits of rubber between the tread cutouts flex more. The tyres heat up through friction because of the soft compound of the rubber and makes them sticky to further deform around the small stones making up the asphalt.Tread

A pure road cycling tyre, tuned for decently smooth surfaces, probably can be as near slick as makes no difference, so a bit like an F1 dry tyre, but as soon as the surface become significantly imperfect some sort of tread can help, especially one where the knobbles (think tiny ones, not MTB or tractor) actually deform as they pass through the contact patch. They can displace water or slime, and grab imperfections. The idea that cutting a tread simply puts fresh air where one wants rubber is too simplistic, for one thing it seems to assume no deformation of the tyre in the contact patch, which even for ‘rock hard’ slicks isn’t quite true, and for modern softer compound tyres run at lower pressures is very untrue.

My point exactly. If the tyre rubber is deforming around the road surface dressing, why the need for tread?
https://www.sheldonbrown.com/tyres.html#tread

Like Cugel I’ve experience wheel-spin when using touring tyres on very steep and very poor surfaces. I have yet to experience it with ‘tiny soft knobbles’ tyres.

In which case your tyres have to much air in them. The only time I've ever experienced wheelspin was on ice. Short of steel studs, nothing grips that.

[Vantage]

F1 tracks are reasonably smooth, don’t incorporate very steep slopes, and if the surface conditions deteriorated to the friction levels found on many low-status roads in winter, let alone off-road, racing would be stopped. Added to which, F1 tyre compounds are designed to run slightly warm, and most leisure cyclists don’t attain speeds that warm their tyres up.

Erm...Monaco? Rumble strips? Add to those the differing surfaces between tracks and they're every bit as unpredictable as public roads. Some can be quite rough such as Silverstone. Then you have the extreme G forces put through those tyres during acceleration, braking and cornering. All done without tread. Tread in fact can make the tyres disintegrate faster. You'll see wet weather F1 tyres fall apart long before their slick counterparts because the bits of rubber between the tread cutouts flex more. The tyres heat up through friction because of the soft compound of the rubber and makes them sticky to further deform around the small stones making up the asphalt.

A pure road cycling tyre, tuned for decently smooth surfaces, probably can be as near slick as makes no difference, so a bit like an F1 dry tyre, but as soon as the surface become significantly imperfect some sort of tread can help, especially one where the knobbles (think tiny ones, not MTB or tractor) actually deform as they pass through the contact patch. They can displace water or slime, and grab imperfections. The idea that cutting a tread simply puts fresh air where one wants rubber is too simplistic, for one thing it seems to assume no deformation of the tyre in the contact patch, which even for ‘rock hard’ slicks isn’t quite true, and for modern softer compound tyres run at lower pressures is very untrue.

My point exactly. If the tyre rubber is deforming around the road surface dressing, why the need for tread?
https://www.sheldonbrown.com/tyres.html#tread

Like Cugel I’ve experience wheel-spin when using touring tyres on very steep and very poor surfaces. I have yet to experience it with ‘tiny soft knobbles’ tyres.

In which case your tyres have to much air in them. The only time I've ever experienced wheelspin was on ice. Short of steel studs, nothing grips that.

[Nearholmer]

My point exactly. If the tyre rubber is deforming around the road surface dressing, why the need for tread?

Contact patch deformation happens at two levels: the gross deformation of the tyre that is a simple (ish) function of the pressure (weight) on the tyre, the pressure within it, and the hardness/suppleness of the tyre, and at a smaller level as the material conforms, or not, to irregularities in the surface.

A continuous surface won’t deform in same the way that lots of little knobbles will.

Get a toothbrush, and brush your teeth with it.

Now, get a solid block of toothbrush bristle material, which I guess might look, if not feel, like a small, white bike brake block, and brush your teeth with that.

The two will act differently.

Clearly a rather extreme example, in that few tyres actually consist of bristles, but knobbles of the kind that Cugel and I are talking about are in effect very short bristles.

As to tyre pressure, when you ride a lot of different surfaces in one ride that is always a compromise (as indeed is tyre width/volume), unless you let down your tyres, and pump them up again every five minutes. What a soft compound tyre with little knobbles allows one to do is get a far better compromise, the knobbles provide that extra bit of bite without taking the pressure down so far that it becomes a huge drag on hard surfaces. It is nigh-on impossible to get an acceptable compromise for multi-surface riding with touring tyres - I know, because I spent years trying.

Looking at Sheldon Brown’s notes, he acknowledges tread as part of what contributes to traction on some surfaces, but he seems to consider only two ‘use cases’: MTB and road, which misses out a lot of literal and figurative middle ground that is of interest to multi-surface riders.

[mig]

the world's F1 teams do use treaded tyres when it's wet.

Surely we've already covered this?!?

[Actually their cars are quite good on slicks until there is substantial build-up - so damp/greasy tracks are fine on slicks. But more importantly:]

CAR tyres aquaplane, being much wider than bike tyres.
Hence the need for tread.

yeah yeah but therefore "Cutting tread into a tyre removes the rubber which would otherwise be providing grip." is not always true for a car (in the wet) nor a bike (climbing its way out of a muddy, leafy or icy rut.)

[Vantage]

My point exactly. If the tyre rubber is deforming around the road surface dressing, why the need for tread?

Contact patch deformation happens at two levels: the gross deformation of the tyre that is a simple (ish) function of the pressure (weight) on the tyre, the pressure within it, and the hardness/suppleness of the tyre, and at a smaller level as the material conforms, or not, to irregularities in the surface.

A continuous surface won’t deform in same the way that lots of little knobbles will.

Get a toothbrush, and brush your teeth with it.

Now, get a solid block of toothbrush bristle material, which I guess might look, if not feel, like a small, white bike brake block, and brush your teeth with that.

The two will act differently.

Clearly a rather extreme example, in that few tyres actually consist of bristles, but knobbles of the kind that Cugel and I are talking about are in effect very short bristles.

As to tyre pressure, when you ride a lot of different surfaces in one ride that is always a compromise (as indeed is tyre width/volume), unless you let down your tyres, and pump them up again every five minutes. What a soft compound tyre with little knobbles allows one to do is get a far better compromise, the knobbles provide that extra bit of bite without taking the pressure down so far that it becomes a huge drag on hard surfaces. It is nigh-on impossible to get an acceptable compromise for multi-surface riding with touring tyres - I know, because I spent years trying.

Looking at Sheldon Brown’s notes, he acknowledges tread as part of what contributes to traction on some surfaces, but he seems to consider only two ‘use cases’: MTB and road, which misses out a lot of literal and figurative middle ground that is of interest to multi-surface riders.

No no no no no no. A toothbrush has an entirely different job to do than a tyre. The two aren't even remotely related.
The tyres that you and cugel are refering to are gravel tyres, not road tyres which the op was asking about.
The nobbles on those tyres are there to bite into the soft ground/loose gravel to provide traction. They have no use on a hard surface such as asphalt or concrete as they cannot bite into that material. They (if long enough) will only bend and flex around giving a jelly like ride quality. Shorter nobbles will do the same but with a less noticeable effect.
It is incredibly easy to find a pressure that your tyres will perform best at. Pump them up to the max recommended pressure and let the air out a little each time you ride until you find the sweet spot. Some tyre will be just plain rubbish using this method as the tyres are just that, rubbish. With a good supple tyre, it will roll effortlessly conforming to every nook and cranny in the road and in my experience and that of others I could mention here, those same tyres will be perfectly capable offroad too except in certain extreme circumstances (deep mud/big rocks).
FWIW, I have a pair of decathlon gravel tyres. Little dinky file like nobbles all over and a set of sticky up sharp nobbles on the edges of said tyres for extra cornering grip. They're pitiful on every surface I've tried them on. My Voyager Hypers? Near bald, half the weight and way more supple. Never once lost grip with those. Even on wet grass I can throw a ton of braking onto the front tyre and it wont slip.

[Nearholmer]

Here’s what the OP said:

Ok, I do have a road bike that absolutely must have blue wall, colour-matched tyres, which usually dictates tyre choice (frivolous, me?); but otherwise, why?

I don’t read that as limiting the discussion to (well surfaced) roads.

In fact, as I said above, an important “…otherwise, why?” in having a bit of tread on the front as well as the back is for climbing out of ruts, where a too smooth front tyre will will refuse to climb the wall of a the rut, leading to one getting literally stuck in a rut and grinding to a halt as it gets deep/narrow enough to trap the cranks.

And, all the things that apply on the most benign of unsurfaced sections apply on the least benign of surfaced sections - sometimes I encounter bits where it is impossible to tell whether it is nominally surfaced or not.

I’m not advocating that “pure roadies” should buy tyres with a pronounced tread, because they probably don’t need that. I’m engaged in what seems to be an endless quest for a multi-surface tyre.

No no no no no no. A toothbrush has an entirely different job to do than a tyre.

That’ll be where I’ve been going wrong all these years then. I always did find it difficult to get the tyre as far as my back teeth.